1. Technical Field
The present disclosure relates to devices and methods for the replacement of joints, and more particularly, to patient-specific hip replacement devices, including methods of manufacturing and using such devices for achieving accurate hip replacement based on computer generated imaging of a patient.
2. Background of the Invention
One known method of treating hip and other joints with arthritis and other medical conditions is to replace surfaces of articulating joints with prosthetic devices through surgical procedures. It is critical that such prosthetic devices are accurately designed and manufactured, and are installed correctly in order to relieve pain and provide an effective treatment method for such ailments. An orthopedic surgeon performing such joint replacement on a patient seeks to ensure, through surgery, adequate placement of the prosthetic and proper reconstruction of the joint being replaced. Prosthetic components used to replace a joint may be placed optimally by templates and jigs according to the unique anatomy of a patient before surgery occurs. A particular patient's bone structure symmetry is one important consideration that a surgeon must consider when performing joint replacement surgery. Additionally, malposition of joint replacement prosthetics can result in premature wear of the bearing surfaces, which may require additional surgeries to correct.
In the case of a hip, the condition of the patient's joint may require a partial or total replacement. A partial hip replacement involves replacing the femoral head (the ball) of the damaged hip joint; however, the acetabulum (the socket) is not replaced in a partial hip replacement surgery. A total hip replacement includes replacing both the femoral head and the acetabulum with prosthetic devices. The femoral head is replaced with a femoral prosthetic that typically includes a head portion and a stem. The stem extends into the femur of the patient and is utilized to secure the femoral device to the femur, with the head portion protruding out from the femur. The acetabulum is then resurfaced and replaced with a cup-shaped acetabular device. The cup-shaped acetabular device provides a bearing surface for the head portion of the femoral prosthetic to allow a desirable amount of range of motion via the joint upon total hip replacement.
To replace the acetabulum effectively, a surgeon will typically enlarge the acetabulum with a reamer machine and reamer head to create a resurfaced cavity to receive a prosthetic acetabular cup, which may or may not be secured by cement or bone screws. One particular issue of concern during the reaming portion of the surgery is that the cutting portion of the reamer is hemispherical while the prosthetic acetabular cup is typically sub-hemispherical. If the acetabulum is reamed too deeply, the prosthetic acetabular cup will be positioned too deep within the reamed cavity. If the acetabulum is reamed too shallowly, the prosthetic acetabular cup will not be positioned deep enough. If the acetabulum is reamed at an improper angle, the prosthetic acetabular cup will not be installed properly. These imperfections can cause malalignment of the prosthetic hip joint. Moreover even if the acetabular bone is properly reamed, it is quite difficult with standard techniques to place the acetabular prosthetic cup. Recent studies, reflect a 50% rate of error in placement of the acetabular cup from an acceptably optimal range of positions when standard techniques are utilized. Thus, accurate reaming of the acetabulum and accurate positioning of the prosthetic acetabular cup are critical.
With the assistance of computer generated data derived from CT, MRI, or other scans, such as X-rays, surgeons can more effectively determine proper alignment and positioning of the prosthetic acetabular cup in a patient through 3D modeling and rendering. While some surgeons use lasers or peripheral guide pins during surgery in an attempt to properly place the prosthetic acetabular cup; however, accuracy and simplicity of existing devices and methods remain limited due to a variety of factors.